Glass or glass ceramic substrates are used in a variety of household appliances or for displays, for example for glass ceramic cooktops in built-in cookers, and also for viewing windows in doors of cooking appliances, baking ovens, or microwave devices. Increasingly, these substrates or surfaces thereof have different partial surface areas or zones accomplishing different functions.
For example, while glass ceramic cooktops originally only included one or more areas adapted as a cooking hob, current cooktops in addition to these cooking hob areas may include partial areas designated for operating the devices. Previously, the various partial areas or sections were mainly visually perceptible. Meanwhile, haptic perception of the different functions is of increasing importance. Haptic perception in particular includes an active sensing of specific areas, sizes, textures, and contours at the surface of an object by touching or palpation. In the decorative sector, haptic properties, for example of surfaces, are known.
DE 20 2009 000 139 U1 describes a switch surface area which has position marks with haptic properties. A relief palpable by a user represents the position marks. This switch surface area is produced by machining such as milling.
Mechanical methods such as polishing or sandblasting are also known. The use of mechanical methods to produce a structure with haptic properties on a substrate surface is often very expensive. Moreover, damage of the surface is likely to occur, which may adversely affect the strength.
EP 1 876 394 A2 describes a glass ceramic cooktop with a sliding strip which has a texture, at least partly, which has a haptic effect. The texture is applied by printing.
DE 10 2007 019 853 A1 describes a method for producing three-dimensional or haptically perceptible information on a planar information carrier. The information is applied to the information carrier by printing.
Applying layers with haptic properties by printing may be significantly more cost-effective, however, a drawback thereof is that these layers often exhibit only low temperature resistance and low mechanical stability. For example, for locally textured layers on a glass ceramic cooktop, which are applied from polyurethane by printing, there is a considerable risk of damage under mechanical stress, due to insufficient bonding to the substrate. Advantageous would be to have a better bonding of the layer to the substrate, for example by fusing in case of glass and glass ceramic substrates.
Furthermore, methods are known for patterning glass surfaces using etching processes, wherein patterning is often accomplished by means of hydrofluoric acid. Such methods are considered to be complex and dangerous, and the variety of texture shapes is limited by the etching process.
WO 2011/085997 describes another method, wherein first a sol-gel layer is applied to a panel, and then a haptically perceptible texture is produced in this layer by means of an embossing tool. Subsequently, the sol-gel layer is cured. This method is also complex, since in addition to the application of the layer it requires a separate work process for embossing.